Auxin herbicides have been widely used as herbicides and include phenoxyacids such as phenoxy-acetic, -propionic and -butyric acid herbicides and their esters; phenyl acid herbicides such as 3,6-dichloro-o-anisic acid (dicamba); pyridyloxy acids such as 3,5,6,pyridyloxy acetic acid; and pyridine carboxylic acids such as 3,6-dichloropyridine-2-carboxylic acid. Phenoxy acetic acid herbicides including 2,4-Dichlorophenoxy acetic acid (2,4-D) and 4-chloro-2-methylphenoxy acetic acid (MCPA) and their esters such as the 2-ethylhexyl and butoxy ethanol esters are used to control broadleaf weeds in crops such as cereals, sugar cane turf pastures and the like. Auxin herbicides are generally of formula

wherein                R is the alcohol portion of the ester or is a salt counter ion such a substituted ammonium counter ion;        A is nitrogen or CH;        X1, X2 and X3 are independently selected from hydrogen, halogen (preferably chloro) and methyl, preferably from hydrogen and chloro and most preferably at least two of X1, X2 and X3 are selected from chloro and methyl;        Y is a bond, oxygen or 1,4-oxyphenoxy;        R1 is selected from hydrogen and methyl and preferably is hydrogen; and        n is from 0 to 3.        
Dicamba is of formula:

The amine salts of the auxin herbicides are in many cases water soluble and aqueous formulations of the amine salts are convenient to use. High concentrations of the amine salts can be prepared thereby potentially minimising the need to transport water in the formulated product while at the same time avoiding or minimising the need to use solvents with the potential disadvantages of flammability, and residue.
At the site of use the concentrate formulations can conveniently be diluted in a spray tank for soil or foliar application.
One of the significant limitations on the formulation and use of the auxin amine salts is the poor solution stability at low temperature particularly in highly concentrated solutions, for example of at least 500 g/L (based on active acid equivalent). This places limitations on the storage and handling of the auxin amine salts, including dicamba, with the result that the loading of salt needs to be lower than would normally be stable due to the propensity to form a significant proportion of crystalline deposits at low temperature which are not always readily redissolved.
The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.